1. Field of the Invention
The present invention relates to a magnetic head for perpendicular magnetic recording that is used for writing data on a recording medium by means of a perpendicular magnetic recording system and a method of manufacturing such a magnetic head, and to a head assembly and a hard disk drive each of which includes the magnetic head for perpendicular magnetic recording.
2. Description of the Related Art
For magnetic read/write devices such as magnetic disk drives, higher recording density has been constantly required to achieve a higher storage capacity and smaller dimensions. Typically, magnetic heads used in magnetic read/write devices are those having a structure in which a reproducing (read) head having a magnetoresistive element (that may be hereinafter called an MR element) for reading and a recording (write) head having an induction-type electromagnetic transducer for writing are stacked on a substrate.
Write heads include those of a longitudinal magnetic recording system wherein signals are magnetized in the direction along the surface of the recording medium (the longitudinal direction) and those of a perpendicular magnetic recording system wherein signals are magnetized in the direction perpendicular to the surface of the recording medium. Recently, the shift from the longitudinal magnetic recording system to the perpendicular magnetic recording system has been promoted in order to achieve higher recording density of magnetic read/write devices.
The write head for the perpendicular magnetic recording system incorporates a coil for generating a magnetic field corresponding to data to be written on a recording medium, and a pole layer for allowing a magnetic flux corresponding to the magnetic field generated by the coil to pass therethrough and generating a write magnetic field for writing the data on the recording medium. The pole layer has an end face located in a medium facing surface, and the width of the end face defines the track width.
As one of magnetic heads for perpendicular magnetic recording, a magnetic head incorporating first and second shields disposed to sandwich a pole layer in between is known, as disclosed in U.S. Pat. No. 7,126,788 B1, U.S. Patent Application Publication 2005/0237665 A1, and U.S. Patent Application Publication 2006/0203384 A1, for example. In this magnetic head, at the medium facing surface, the end face of the first shield is located backward of the end face of the pole layer along the direction of travel of the recording medium with a specific distance provided therebetween. The end face of the second shield is located forward of the end face of the pole layer along the direction of travel of the recording medium with a specific distance provided therebetween. The first and second shields have a function of preventing a magnetic flux from reaching the recording medium, the flux having been generated from the end face of the pole layer and expanding in directions except the direction orthogonal to the surface of the recording medium. The magnetic head incorporating such first and second shields makes it possible to achieve a further improvement in recording density.
Consideration will now be given to a method of forming a first shield of a magnetic head in which the first shield is located closer to the substrate than the second shield. As such a magnetic head, one having a structure in which the first shield is disposed on a magnetic layer disposed to sandwich a coil between itself and the pole layer, as disclosed in U.S. Patent Application Publication 2005/0237665 A1 or U.S. Patent Application Publication 2006/0252620 A1, for example. The first shield of the magnetic head having such a structure is formed by frame plating, for example. In this method, a photoresist layer is first formed on the magnetic layer, and the photoresist layer is patterned by photolithography to form a frame. The frame has a groove having a shape corresponding to the shape of the first shield to be formed. Next, the first shield is formed by plating in the groove of the frame.
The shape of the first shield has influences on write characteristics. For example, the length of the top surface of the first shield opposed to the pole layer taken in the direction orthogonal to the medium facing surface has influences on the capability of a function of the first shield, that is, a function of taking in a magnetic flux generated from the end face of the pole layer and expanding in directions other than the direction orthogonal to the surface of the recording medium. It is therefore required to control the shape of the first shield with precision.
The thickness of the first shield is defined by factors such as the distance between the read head and the write head determined in accordance with the specifications of the magnetic read/write apparatus, or the distance between the magnetic layer and the pole layer required for placing components other than the first shield, such as a coil, in the region between the magnetic layer and the pole layer where the first shield is disposed.
To form the first shield having a desired thickness by frame plating, it is required to form a frame thicker than the first shield. Since this frame is formed by photolithography, it becomes harder to form the groove of the frame with precision as the thickness of the frame is increased. Therefore, the thicker the frame, the harder it becomes to control the shape of the first shield with precision.